Imaging of hepatic steatosis and fatty sparing: a review

Radiology has gained importance in the noninvasive diagnosis of hepatic steatosis. Ultrasonography is usually the first imaging modality for the evaluation of hepatic steatosis. Unenhanced computed tomography (CT) with or without dual kVp measurement and magnetic resonance imaging (MRI) with in- and out-of-phase sequence can allow objective evaluation of hepatic steatosis. However, none of the imaging modalities can differentiate nonalcoholic steatohepatitis/fatty liver disease from simple steatosis. Evaluation of hepatic steatosis is important in donor evaluation before orthotopic liver transplantation and hepatic surgery. Recently, one-stop-shop evaluation of potential liver donors has become possible by CT and MRI, integrating vascular, parenchymal, volume, and steatosis evaluation. Moreover, hepatic steatosis (diffuse, multinodular, focal, subcortical, perilesional, intralesional, periportal, and perivenular), hypersteatosis and sparing (geographic, nodular, and perilesional or peritumoral) can cause diagnostic problems as a pseudotumor, particularly in the evaluation of oncology patients. Liver MRI is used as a problem-solving tool in these patients. In this review, we discuss the current role of radiology in diagnosing and quantifying hepatic steatosis and solutions for diagnostic problems associated with fatty infiltration and sparing.